Over the past 25 years, the Nipah virus has shifted from a little‑known zoonotic infection to one of the most closely watched emerging pathogens in global health.

First recognised in Southeast Asia in the late 1990s, the virus has repeatedly demonstrated its ability to cross species barriers, cause severe disease in humans, and produce strikingly high fatality rates.

“Nipah virus is quiet, persistent, and unforgiving, and preparedness remains the best defence”

Each new outbreak, however small, reinforces concerns among scientists and public health authorities that Nipah virus remains a persistent and unpredictable threat.

That concern was underscored again in January 2026, when India reported two new laboratory‑confirmed cases of Nipah virus infection in West Bengal. On 26 January 2026, India’s National International Health Regulations Focal Point formally notified the World Health Organization of the event. The cases involved two healthcare workers employed at the same private hospital in Barasat, in the North 24 Parganas district, raising immediate alarms about possible healthcare‑associated transmission.

Laboratory confirmation was provided by the National Institute of Virology in Pune on 13 January 2026, using both reverse transcription polymerase chain reaction testing and enzyme‑linked immunosorbent assay. Both patients, a female nurse and a male nurse aged between 20 and 30 years, developed symptoms consistent with severe Nipah virus infection in late December 2025 and were admitted to hospital in early January. One patient experienced critical illness and remained on mechanical ventilation as of 21 January, while the other suffered severe neurological disease but subsequently showed clinical improvement.

“…at least 756 confirmed human cases have now been reported worldwide, with more than 435 deaths. This keeps the global average case fatality rate close to 60 percent, a figure that few other emerging viruses approach.“

Indian health authorities responded rapidly. More than 190 contacts were identified, including healthcare workers and community members. All were tested for Nipah virus with support from a mobile biosafety level‑3 laboratory deployed by the National Institute of Virology. Every contact tested negative, and no additional cases have been detected to date.

Enhanced surveillance and strict infection prevention and control measures remain in place as investigations into the source of exposure continue. This event marks the third recorded Nipah virus outbreak in West Bengal, following earlier outbreaks in Siliguri in 2001 and Nadia in 2007.

The World Health Organization has assessed the risk posed by this event as moderate at the sub‑national level, and low at the national, regional, and global levels. Even so, the episode highlights how quickly Nipah virus can reappear, often in settings where healthcare workers are on the front line of exposure.

With the addition of these two cases, the global picture of Nipah virus infection becomes slightly but significantly grimmer. From its first emergence in 1998 through January 2026, at least 756 confirmed human cases have now been reported worldwide, with more than 435 deaths. This keeps the global average case fatality rate close to 60 percent, a figure that few other emerging viruses approach. Confirmed human infections have been documented in five countries: Bangladesh, India, Malaysia, Singapore, and the Philippines.

The virus first came to global attention during the 1998–1999 outbreak in Malaysia, which primarily affected pig farmers and abattoir workers. Pigs acted as efficient intermediate hosts after becoming infected by fruit bats, enabling widespread transmission to humans. Nearly 300 people were infected across Malaysia and Singapore, and more than 100 died. Large‑scale culling of pigs and movement restrictions eventually halted the outbreak. Since then, no further human cases have been reported in either country.

The epidemiology of Nipah virus shifted in the early 2000s, when outbreaks began appearing in South Asia. Bangladesh reported its first cases in 2001, followed soon after by India. Unlike the Malaysian outbreak, these events were not linked to pigs or other obvious intermediate hosts. Instead, investigations identified the consumption of raw date palm sap and fruit contaminated with bat saliva or urine as the primary sources of infection.

Bangladesh has since become the country most affected by Nipah virus. Outbreaks occur almost every year, particularly during the winter months when date palm sap is harvested. As of early 2026, Bangladesh has recorded more than 340 confirmed cases and over 240 deaths, accounting for roughly 45 percent of global cases and more than half of all reported deaths. Case fatality rates consistently exceed 70 percent, reflecting both the virulence of the virus and ongoing challenges in early diagnosis and access to advanced supportive care.

“There is also concern about viral evolution. Nipah virus is genetically diverse and capable of change. While sustained human‑to‑human transmission has so far been limited, researchers caution that adaptation could alter that balance”

India’s experience has been marked by fewer cases but similarly high fatality rates. Including the two newly reported cases in West Bengal, India has now documented more than 104 confirmed infections and approximately 76 deaths since 2001. Outbreaks have occurred in West Bengal and Kerala, with several events in Kerala over the past decade drawing intense media and scientific attention. Swift public health responses in those outbreaks, including rapid isolation and aggressive contact tracing, helped prevent wider spread, but mortality remained high.

In Southeast Asia beyond Malaysia and Singapore, the Philippines reported a notable outbreak in 2014. That event was linked to infected horses, which served as intermediate hosts. People who handled or consumed meat from sick animals later developed severe disease. More than half of the confirmed cases died, reinforcing fears that Nipah virus can exploit multiple animal species to reach humans.

One of the most concerning aspects of Nipah virus epidemiology is the stark regional variation in fatality rates and transmission patterns. Outbreaks linked to animal intermediates, such as pigs or horses, have generally shown lower fatality rates than those involving direct bat‑to‑human transmission.

Scientists attribute part of this difference to genetic variation between viral strains. Two closely related clades have been identified, one associated with outbreaks in Bangladesh and India, and another linked to Malaysia, Singapore, and the Philippines. Subtle genetic differences may influence how efficiently the virus infects human cells and how severe the resulting disease becomes.

Transmission routes also differ. In Bangladesh and parts of India, person‑to‑person transmission has been documented, including among family members and healthcare workers. The recent West Bengal cases, involving two nurses from the same hospital, inevitably revive concerns about healthcare‑associated spread, even though no secondary cases have been detected so far.

Despite improvements in surveillance and public awareness, Nipah virus continues to exploit gaps. Mild or asymptomatic infections may go undetected, particularly in rural or resource‑constrained settings. This means official case counts almost certainly underestimate the true scale of infection. The lack of licensed medicines or vaccines further complicates control efforts. Treatment remains supportive, focused on managing respiratory failure, neurological complications, and secondary infections. Evidence suggests that early supportive care improves survival, but options remain limited.

Beyond the immediate outbreaks, experts continue to warn about broader risks. Fruit bats carrying Nipah virus or related henipaviruses are distributed across large parts of Asia, the Pacific, and Africa.

Antibodies reacting to Nipah virus have been detected in bats in numerous countries, and viral genetic material has been identified in several regions that have never reported human cases. Environmental disruption, deforestation, urban expansion, and climate change are increasing contact between bats, domestic animals, and people, creating more opportunities for spillover.

There is also concern about viral evolution. Nipah virus is genetically diverse and capable of change. While sustained human‑to‑human transmission has so far been limited, researchers caution that adaptation could alter that balance. The lessons of recent pandemics have heightened sensitivity to such possibilities.

For now, global health agencies continue to classify the overall risk from Nipah virus as low at the global level. Yet each new outbreak, including the recent cases in West Bengal, serves as a reminder that vigilance cannot wane. Strengthened surveillance, rapid diagnostics, strict infection prevention in healthcare settings, and sustained investment in research are essential.

After more than two decades, Nipah virus remains rare but relentlessly dangerous. Its high fatality rate, complex transmission pathways, and expanding ecological footprint ensure it will remain under close scrutiny.

The latest cases in India do not signal a global crisis, but they do reinforce a simple message shared by scientists and public health experts alike: Nipah virus is quiet, persistent, and unforgiving, and preparedness remains the best defence.

By Tony Y, Editor-in-chief, PP Health Malaysia (PPHM). Tony is a former medical research scientist and consultant based in University of Malaya. He had published over 20+ ISI international peer-reviewed scientific journals.